Tricalcium aluminate (C3A)

Tricalcium aluminate (C3A) is one of the main compounds present in cement. It reacts with water and contributes to the initial setting and early strength development of cement. Let us understand each option in detail to see why option A is the correct answer.

a) Reacts fast with water
Tricalcium aluminate (C3A) reacts very quickly with water compared to other compounds present in cement. This reaction is known as hydration, where water molecules break down and bond with the C3A compound. This rapid reaction leads to the formation of various hydration products, such as calcium aluminate hydrates, which contribute to the hardening and setting of cement.

b) Generates less heat of hydration
Tricalcium aluminate (C3A) actually generates a significant amount of heat during hydration. When C3A comes in contact with water, it undergoes an exothermic reaction, releasing heat. This heat of hydration can be quite high compared to other cement compounds. Therefore, option B is incorrect.

c) Causes initial setting and early strength of cement
Tricalcium aluminate (C3A) plays a crucial role in the initial setting and early strength development of cement. During hydration, the C3A compound forms calcium aluminate hydrates, which contribute to the formation of a solid matrix. This matrix provides the initial stiffness and strength to the cement, allowing it to set and harden. Therefore, option C is correct.

d) Does not contribute to developing ultimate strength
Tricalcium aluminate (C3A) does contribute to the development of ultimate strength in cement. While it is true that other compounds like tricalcium silicate (C3S) and dicalcium silicate (C2S) play a more significant role in the long-term strength of cement, C3A still contributes to the overall strength. The hydration products formed by C3A provide a durable matrix that contributes to the ultimate strength of the cement. Therefore, option D is incorrect.

In conclusion, the correct answer is option A - Tricalcium aluminate (C3A) reacts fast with water. It undergoes rapid hydration, leading to the initial setting and early strength development of cement.